The present invention relates to a flow control valve used for discharging and controlling fluids such as high corrosive chemical liquid or ultra pure water in a semiconductor manufacturing device or the like.
As a flow control valve used for discharging and controlling fluids such as high corrosive chemical liquid or ultra pure water in a semiconductor manufacturing device or the like, there has been known those disclosed for example in Patent Document 1 and Patent Document 2. FIG. 16 is a sectional view of a valve unit 100 of Patent Document 1. FIG. 25 is a sectional view of a flow regulating mechanism 300 of Patent Document 2.
In the valve unit 100 of Patent Document 1 shown in FIG. 16, a flow control valve 110 and an opening/closing valve 101 are mounted in a unit block 102. The flow control valve 110 is a diaphragm valve provided with a differential screw.
The flow control valve 110 is provided with a spindle 112 inserted in a base pipe 111 fixed to the unit block 102. The spindle 112 is movable upward and downward but not rotatable. A diaphragm 113 is fixed at a lower end of the spindle 112, and a spring 115 is mounted in a contracted state between the base pipe 111 and the spindle 112. This spring 115 constantly exerts a force to press the diaphragm 113 down toward a valve seat 114 which is mounted on the unit block 102. The base pipe 111 is exteriorly covered with an outer sleeve 116, and an outer thread portion 117 is provided between the base pipe 111 and the outer sleeve 116 to engage them. In the outer sleeve 116, an inner sleeve 119 inserted between the base pipe 111 and the spindle 112 is fastened with a fixing screw 118. Between the inner sleeve 119 and the spindle 112, an inner thread portion 120 is provided between the inner sleeve 119 and the spindle 112 to engage them. The flow control valve 110 includes a differential screw provided by the outer sleeve 116 and the inner sleeve 119.
In this flow control valve 110, when the outer sleeve 116 and the inner sleeve 119 are rotated integrally, the spindle 112 inside the base pipe 111 is moved axially upward or downward in the figure by a pitch difference between the outer thread portion 117 and the inner thread portion 120, so that a position of the diaphragm 113 is adjusted. The flow control valve 110 includes a cover 121 covering over the outer sleeve 16 so as not to be touched by an operator and the like in order to maintain a position of the differential screw after the adjustment.
The flow regulating mechanism 300 of Patent Document 2 shown in FIG. 25 comprises a valve main body 301 and a direct acting member 302. The direct acting member 302 is movable forward and backward (upward and downward in the figure) in the valve main body 301 by a screw motion of an adjustment screw 303 to adjust a position of a needle member 304 which is mounted at a lower end of the direct acting member 302. The needle member 304 is inserted in an orifice 305 of the valve main body 301 to be movable forward and backward to regulate an opening degree of the orifice 305 to regulate a flow rate of fluid flowing from a fluid inlet port 306 to a fluid outlet port 307. The adjustment screw 303 is formed with a first screw portion 309 threadedly engaging with a groove 308 of the valve main body 301 and a second screw portion 311 threadedly engaging with an inner screw portion 310 of the direct acting member 302. When the first screw portion 309 is rotated, its rotation force is transmitted to the direct acting member 302 through the second screw portion 311. The direct acting member 302 is locked by a pin 313 which is firmly attached to the valve main body 301 and received in a groove 312 of the direct acting member 302 to prevent rotation of the direct acting member 302. The rotation force transmitted from the second screw portion 311 is converted into a driving force to linearly axially move the direct acting member 302, thereby moving the needle member 304 forward and backward in accordance with a pitch of the second screw portion 311. In the flow regulating mechanism 300, minute control can be achieved accurately by a difference between a pitch P1 of the first screw portion 309 and a pitch P2 of the second screw portion 311.
Patent Document 1: Japanese Unexamined Patent Application No. 2001-263507A (Paragraphs [0014] to [0019], and FIG. 2)
Patent Document 2: Japanese Unexamined Patent Application No. 11 (1999)-051217A